Spigot Configuration Boilerplate for Kotlin

ConfigurationProperty.kt

package de.nycode.fynixlobby.config

import de.nycode.fynixlobby.PluginInstance
import de.nycode.fynixlobby.config.feature.LobbyWeatherType
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

typealias ChangeListener<T> = (newValue: T) -> Unit

fun config(path: String, default: String): ConfigurationProperty<String> =
    ConfigurationProperty(path, { it }, default)

fun <T> config(path: String, default: T, transform: (String) -> T): ConfigurationProperty<T> =
    ConfigurationProperty(path, transform, default)

class ConfigurationProperty<T>(
    private val configPath: String,
    private val transform: (String) -> T?,
    private val default: T,
    private var onChange: ChangeListener<T> = { _ -> }
) : ReadWriteProperty<Any, T> {

    fun onChange(listener: ChangeListener<T>): ConfigurationProperty<T> {
        onChange = listener
        return this
    }

    init {
        if (PluginInstance.config.get(configPath) == null) {
            PluginInstance.config.set(configPath, default)
            PluginInstance.saveDefaultConfig()
        }
    }

    override fun setValue(thisRef: Any, property: KProperty<*>, value: T) {
        PluginInstance.config.set(configPath, value)
        onChange(value)
    }

    override fun getValue(thisRef: Any, property: KProperty<*>): T {
        return transform(PluginInstance.config.getString(configPath) ?: return default) ?: default
    }
}